Electric pneumatic control valve of pneumatic control valve failure analysis

Pneumatic control valve when the input 4 ~ 20 mA signal, pneumatic control valve stem can be within the rated stroke upper and lower moving freely according to the signal change. If can't normal movement, may have the following fault operation hand wheel paresthesia feel too light, may be the handwheel card pin fall off or break; Feel too heavy or spin. Reducer and foreign body in it; The valve core and the bushing or stuck with the valve seat; Stem severe bending. Enter 4 ~ 20 mA signal, pneumatic control valve is not action, that may be wrong wiring system, split-phase motor capacitor CD damage, electrical wiring, valve core loss or stem fracture (open While actuators have) Input 4 ~ 20 mA signal, pneumatic control valve walk not after the trip may be rated differential transformer location is not good, diode D701 ~ D712 damage of individual, triode BG701 damage.